ADMINISTRATOR
enqueue named ENQUEUE1
for over six minutes. It looks
at the blockers and determines
that B2/004E2A90 on SYS2
is the top blocker. Runtime
Diagnostics then invokes
itself on SYS2 and requests
analysis of B2/004E2A90.
It discovers that it's waiting
for a latch called SYSTEST.
LATCH_TESTSET on SYS2 that's
held by B3/004FF048 on SYS2.
Runtime Diagnostics follows
B3/004FF048 on SYS2 even
if B2/004E2A90 hasn't been
waiting the minimum time. As it
analyzes B3/004FF048 on SYS2,
any events found are returned to
SYS1 for additional analysis and
correlation.
Correlated Events
Prior to z/OS 2.3, all events were
output individually. Runtime
Diagnostics now combines
related events into correlated
events to determine which action
to take. The last event found is
called the final event.
If the final event is a contention
event, the blocker might be
experiencing a problem that
Runtime Diagnostics doesn't
identify. In that case, Runtime
Diagnostic's critical message
analysis function will be
performed for the system for
which Runtime Diagnostics was
originally invoked as well as for
every system for which the final
event was a contention event.
The critical, component messages
found for the top blocker's system
in conjunction with the final event
should aid in your investigation
and resolution of the problem.
If the final event only has one
job name (e.g., a LOOP event), that
issue is probably the root of the
problem, at least of the problems
that Runtime Diagnostics
identifies, and the ACTION:
specified should be taken to
resolve the correlated events.
Figure 1: Following a Top Blocker
52 // MARCH/APRIL 2018 ibmsystemsmag.com
W
In z/OS V2.3,
Runtime
Diagnostics
not only finds
deadlocks on the
system for which
it was invoked,
but also across
systems, and
between GRS
enqueues and
latches
Figure 2 (page 53) shows
output from Runtime Diagnostics
using the example from
Figure 1 with the addition
that B3/004FF048 on SYS2
was found to be looping. The
first event found in Runtime
Diagnostic's processing, the
enqueue contention for resource
ENQUEUE1, is the first related
event and caused Runtime
Diagnostics to follow the top
blocker, B2/00432A90 on
SYS2. Notice that B2/004E2A90
on SYS2 is a waiter for the
second related event, the latch
contention event. The top blocker
B3/004FF048 on SYS2 for the
latch contention event was then
followed and discovered to be
looping, which is the final event.
Taking action for this final event
should cause the resolution of all
events in this correlated event.
Other waiters are listed for
contention events because they
might also be affected by the